Immiscible alloys with a miscibility gap in the liquid state are scientifically important and can offer unusual properties that may be useful for a wide range of applications, such as bearings, electrical contacts and switches, superconductors, and Giant Magnetoresistive (GMR) materials. However, it is challenging to effectively control the diffusional and colliding growth of immiscible minority droplets in an immiscible alloy during cooling in order to obtain a uniform dispersion of micrometer-sized or nanometer-sized minority phases in the alloy liquids and/or in the solids.
For an immiscible alloy, above the miscibility gap the alloy components are completely miscible as a single solution. If this single phase liquid is cooled down into the miscibility gap, the single phase liquid becomes unstable, nucleating and then separating into two liquid phases with distinct properties. The diffusion coefficient in alloy liquids is generally very high and, thus, after nucleation, the minority liquid droplets can grow very rapidly to become large droplets, which are prone to coagulation (colliding growth) and segregation.
Conventional techniques for forming two-phase alloys utilize a rapid cooling rate to reduce the time for the diffusional and colliding growth of the minority liquid phases. Unfortunately, a high temperature gradient during rapid cooling generally induces severe thermo-capillary forces that push the droplets to the hotter region, making uniform dispersion and colliding growth control of the minority droplets extremely difficult to achieve. Moreover, the use of high cooling rates restricts the size and complexity of the fabricated products, severely limiting their penetration into technical applications.